Low power factor line resonator



Dec. 28, 1937. J. w. CONKLIN ET AL 2,103,515

LOW POWER FACTOR LINE RESONATOR Filed Aug. 31, 1935 2 Sheets-Sheet l X wIVIIIIIIlIIIIIIII/IIIIlIIIIIII/IIIIM/flWflI/IIIIIIII/IIIW/IWIII/lWill/011) I INVENTORS JAMES W. CONKLIN LUDWIG A.BATTERMANI N S F W H- k ATTORNEY Dec. 28, 1937. J. w. CONKLIN ET AL 2,103,515

LOW POWER FACTOR LINE RESONATOR Filed Aug. 31, 1935 2 Sheets-Sheet 2 mmmmwmmmm VIIIIIIIIIHIIIIIIIIII4 INVENTORS JAMES W. CONKLIN LUDWIG A.BATTERMANN ATTORNEY Patented Dec. 28, 1937 UNITED STATES PATENT OFFICE LOW POWER FACTOR LINE RESONATOR Application August 31, 1935, Serial No. 38,695

15 Claims.

This invention relates to improvements in electrical resonators, and particularly to the low loss concentric conductor transmission line type of resonator, such as is used for frequency control.

It is known that the resonant frequency of low power factor concentric conductor transmission line resonators depends to an extent on the projected length of the inner conductor on the outer conductor. Advantage is taken of this feature in stabilizing the resonant frequency of the line against changes due to variations in temperature by maintaining the projected length of the inner conductor constant. This is achieved by providing the free end of said inner conductor with a mechanically extensible and electrically continuous section, and maintaining the overall length of said inner conductor constant by means of an internal fixed rod of low temperature coefficient material. Such an arrangement for 20 maintaining the overall length of the inner conductor constant is described more completely in copending applications Serial Nos. 1,489 and 5,058 (now United States Patent No. 2,077,800, granted April 20, 1937), filed January 12 and February 3, 1935, respectively, by F. H. Kroger, to which reference is herein made. A disadvantage of this method of controlling the effective length of the concentric line lies in the fact that the line is not very readily designed within the tolerance limits required for operation and it is usually necessary tocletermine the correct length of the inner conductor of the frequency controlling line by actual operating tests. Heretofore, final adjustments have been accomplished by providing interchangeable or adjustable end sections on the inner conductors, as shown in United States Patent No. 2,077,800, supra. Because of the high radio frequency voltages present on the end of the inner conductor and because the introduction of any adjusting tool will affect the resonant frequency, adjustments cannot be made While the device is in operation. It is further necessary to have the inner conductor easily accessible for such adjustment, a requirement which is not always convenient.

The primary object of the present invention is to overcome the foregoing disadvantages, and to provide an improved way of effecting fine adjustment of the resonant frequency of such lines.

A further object is to provide a means of adjustment which may be used while the line is in operation.

A still further object of the invention is to provide a means of adjustment which may be calibrated, as with a scale and pointer for convenience in setting to any desired operating frequency.

Another object is to incorporate with the adjusting means, means for holding the effective electrical constants of the circuit independent of temperature variations.

In general, the invention comprises, in combination, a concentric conductor transmission line type of electrical resonator consisting of an outer conductor and an inner conductor, the inner conductor being mechanically supported and conductively coupled to the outer conductor at one end, and the inner conductor having at its free end a mechanically extensible section cou- Dled to it conductively by means of a bellows, or capacitively by means of concentric sleeves, or both, the extensible section being controlled by a rod of suitable low temperature coefficient material mounted internally of the inner conductor and longitudinally adjustable with respect to the inner conductor, and external means for controlling the motion of the rod, and, optionally, means for registering the movement of the rod or its adjusting means, as by a scale and pointer or calibrations as on a micrometer screw.

The principles of construction and operation of this invention may be better understood from the accompanying drawings which illustrate, in Figs. 1 to 4, different embodiments of the invention.

Referring to Fig, 1, there is shown a low power factor concentric transmission line of the type to which this invention is applicable, comprising an inner conductor 3 and an outer conductor I, both conductors being joined together at one of their adjacent ends by an end plate 2. For maintaining the overall length of the inner conductor 3 substantially constant despite temperature fluctuations, there is provided, in accordance with known arrangements, an extensible metallic bellows 5 having an end plate 4 movable with the bellows, and an invar control rod 0 of low temperature coeiiicient connected to the end plate 4 and extending substantially the entire length of the inner conductor. Bellows 5 is arranged to open and close in response to any increase or decrease in length of tube 3 due to change in temperature. Invar rod 8 thus maintains the overall length of the inner conductor including the bellows constant with change in temperature. In accordance with the invention, there is provided a spindle l which is restrained from rotating by pins 8 insertable in the end plate 2,-

this spindle engaging invar rod 6 for extending same. End plate 2 may be of any suitable material althoughit is preferred to use copper, as described in copending application Serial No. 1,489, supra. For obtaining fine adjustment of the inner conductor there is also provided a micrometer adjusting screw 9 which has a position scale I l adjacent to the flange I0 forming part of the screw 9. A bearing washer l2 and a spring washer I3 is provided in the manner indicatedin the drawings, toeliminate end play, and nuts 14 and I5 are-employed to act asthrust collars on the spindle. For removing end play from the micrometer adjusting screw 9, there is also provided a threaded collar I6. A cover plate I! for the outer conductor I merely serves to prevent dust and foreign substances from entering the inside of the outer conductor.

In operation, the resonant frequency of the control line |-3 is adjusted by rotating the micrometer screw flange l0 which carries the spindle 1 and rod 6, moving rod 6 in or-out and with .a consequent expansion or contraction of the bellows 5. After adjustment, the invar rod maintains thelength of the inner. conductor substantially independent of temperature variations. It will be understood, of course, that the line resonator provided with thefine adjustment device of .the invention maybe used in any circuit in which an unadjustable line of the same type y be employed.

Fig. 2 shows asomewhat simpler variation in which-the extensiblesectionis formed by acapacity sleeve 20 in the samelmanner as is described in United .States .Patent No. 2,077,800, supra, and the adjustment .is. here accomplished by asingle bearing nut I 8 working against a spring l9 which also ,removes end play between the spindle land the rod of low temperature coefficient ,6. Since the electrostatic capacity hetween'the inner conducting .tube 3 and the sleeve 20 gives negligible reactance compared to the line reactance and the free end, the variations in length of inner conductor 3 withchangein temperature will not aifect the electrical constants determining the frequency. Inconsequence, because of the ,very low temperature coeflicient of rod .6, the electrical-lengthof theconcentricline, as determined by the overall ,distancefrom the end plate '2 to the top of sleeve v 21) will remain practically constant and the resonant frequency of the line will remain fixed.

Fig. 3 is a, still simplerform of the invention wherein the moving .rod 6 extends through a simplebearing 2| in the end plate2, and is operated by direct effort and locked in the desired position by a set screw 22. This type of arrangement, however, is not capable of exact adjustnot shown. A plurality of screws 24 may be used for setting .the position of the flange 23 and spindle l .in a permanent manner once the adjustment. has been determined, and in this way the expense of fitting each resonator with a micrometer adjustment may be eliminated.

.It will be understoodthat the invention is not limited .to the precise arrangements that have been described in connection with Figs. 1 to 4,

since various other embodiments may at once suggest themselves to those skilled in the art, and be within the scope of the present invention. For example, motion of the adjusting rod may be controlled either by electrical means or by mechanical means from a remote point.

'From What has been set forth above, it will also be understood that the term line resonator appearing in the specification and appended claims, designates a circuit comprising inner and outer conductors, which circuit is equivalent to a tuned circuit resonating at a particular frequency. Such a line resonator may be used to control the frequency of an oscillator, or to replace the conventional tank circuit in various known arrangements.

What'is claimed is:

1. ;-A-line resonator comprising inner and outer conductors mechanically fixed in position with respect to one another at one of their adjacent ends, an element which is adjustable inlength with respect to the free-end of said inner conductor coupled thereto, a rod of low temperature coeiiicient secured to said element and extending substantially the length of and within said inner conductor for maintaining the effective overall length of said inner conductor and element constant with respect to said outer conductor despite temperature fluctuations, and means external of saidconductors and mechanically linked to said rod for adjustingthe effective length of said inner conductor including said element.

,2. .A line resonator comprising inner and outer conductors mechanically fixed in position With respect toone another at one of .their adjacent ends, an extensible bellows attached to the free end of ,said inner conductorand a rod of low temperature coeiilcient extending substantially the length of and within said'inner conductor and mechanically connected to said bellows for maintaining the efiective' overall length of said inner conductor and bellows substantially constant with respect to said outer conductor, despite temperature fluctuations, and means external of said conductors and mechanically linked in to said rod foradjusting the eifective length of said inner conductor including said bellows.

3. A line resonator comprising inner and outer conductors mechanically fixed in position with respect .toone another at one of their adjacent ends, a sleeve concentrically arranged with respect, and .capacitively coupled, to the free end of said inner conductor, and a rod of low temperature coefficient mechanically connected to said sleeve for maintaining the eifective overall length of said inner conductor and sleeve constant with .respect to said outer'conductor despite temperature fiuctuations, and means external of said conductorsand mechanically linked to said rod for adjusting the position of said sleeve with respect to the free end of said inner conductor.

4. Apparatus in accordance with claim 1, characterized in this that said means comprises an adjusting screw arrangement engaging said rod and responsive to movement for movingsaid rod.

5. The combination with a line resonator comprisinginner and outer conductors mechanically fixed in position with respect to one another at one of their adjacent ends, an electrically conductive element physically positioned to increase the length of said innerconductor and extending beyond the free end of said inner conductor, a rod of .low temperature coeificient connected to said element and extending substantially the length of and within said inner conductor for maintaining the effective overall length of said inner conductor and element with respect to said outer conductor constant despite temperature fluctuations, of an adjusting screw external of said conductors and mechanically linked to said rod for adjusting the effective length of said inner conductor, and a position scale adjacent said screw for enabling the determination of the degree of adjustment of said screw.

6. A low power factor line resonator comprising inner and outer concentric conductors, a metallic end plate directly connecting together said conductors at one of their adjacent ends, an electrically conductive element physically positioned to increase the length of said inner conductor and extending beyond the free end of said inner conductor, a rod of low temperature coefficient connected to said element extending substantially the length of and within said inner conductor for maintaining the overall effective length of said inner conductor and element constant with respect to said outer conductor despite temperature fluctuations, said end plate having an aperture therein arranged coaxially with respect to said rod, and an adjusting screw external of said end plate and mechanically linked to said rod through said aperture for adjusting the said rod whereby the effective length of said inner conductor including said element is determined.

7. Apparatus in accordance with claim 6, including a flange connected to said screw and movable therewith, and a position scale attached to said end plate and adjacent said flange for enabling the determination of the degree of adjustrnent of said screw.

8. A low power factor line resonator comprising inner and outer concentric conductors, a metallic end plate directly connecting together said conductors at one of their adjacent ends, an electrically conductive element physically positioned to increase the length of said inner conductor and extending beyond the free end of said inner conductor, a rod of low temperature coeflicient connected to said element and extending substantially the length of and within said inner conductor for maintaining the overall effective length of said inner conductor constant with respect to said outer conductor despite temperature fluctuations, said end plate having an aperture therein arranged coaxially with respect to said rod, and an adjusting screw external of said end plate and extending through said aperture for engaging the end of said rod whereby the effective overall length of said rod is adjusted.

9. A low power factor line resonator comprising inner and outer concentric conductors, a metallic end plate directly connecting together said conductors at one of their adjacent ends, an electrically conductive element physically positioned to increase the length of said inner conductor and extending beyond the free end of said inner conductor, a rod of low temperature coefficient connected to said element and extending substantially the length of and within said inner conductor for maintaining the overall effective length of said inner conductor and element constant with respect to said outer conductor despite temperature fluctuations, said end plate having an aperture therein arranged coaxially with respect to said rod, and an adjustable element external of said end plate. and mechanically linked to the end of said rod through said aperture for adjusting the position of said rod with respect to said end plate, and a resilient spring between said adjustable element and said end of said rod to which said adjustable element is mechanically linked.

10. A low power factor resonator comprising inner and outer conductors, an end plate connecting said conductors at one of their adjacent ends, an electrically conductive element physically positioned to increase th length of said inner conductor and extending beyond the free end of said inner conductor, said end plate having an aperture, a rod of low temperature coefficient connected to said element, said rod being within and extending throughout the length of said inner conductor for maintaining constant the overall length of said inner conductor and element with respect to said outer conductor despite temperature fluctuations, said rod extending through the aperture of said end plate, a flange for said end plate, and a screw movable in said flange and adapted to exert pressure on said rod for enabling adjustment of the length of said rod.

11. A line resonator comprising inner and outer hollow conductors electrically coupled together at one of their adjacent ends, an electrically conductive element physically positioned to increase the length of said inner conductor and extending beyond the free end of said inner conductor, a rod of low temperature coefficient extending substantially the length of and within said inner conductor and connected to said element and means externally of said conductors and linked to said rod for adjusting the effective length of said inner conductor including said conductive element.

12. A line resonator comprising inner and outer hollow concentric conductors coupled together at one of their adjacent ends, a mechanically extensible bellows connected to said inner conductor along the length thereof, a rod of low temperature coefficient of expansion located within said inner conductor and supported at substantially one end from a point near said one of the adjacent ends of said concentric conductors, said rod being connected at its other end to said bellows, and means external of said line resonator for enabling longitudinal movement of said rod within said inner conductor.

13. A line resonator comprising inner and outer hollow concentric conductors, an end plate mechanically coupling said conductors together at one of their adjacent ends, a mechanically extensible bellows connected to said inner conductor along the length thereof, a rod of low temperature coefhcient of expansion located within said inner conductor and supported at one end from said end plate, the other end of said rod being connected to said bellows, whereby the efifective overall length of said inner conductor including bellows is maintained substantially constant despite temperature fluctuations, and means external of said line resonator and mechanically linked to said rod for adjusting the effective overall length of said inner conductor.

14. A line resonator comprising inner and out er hollow concentric conductors, an end plate mechanically coupling said conductors together at one of their adjacent ends, a sleeve concentrically arranged with respect to and surrounding the other end of said inner conductor, said sleeve by virtue of its spacing being capacitively coupled to said inner conductor, a rod of low temperature coefiicient of expansion located within said inner conductor and supported at one end from said end plate, the other end of efiicient of expansion located Within and lengthwise of said inner conductor, said rod being linked at one end to said collapsible element and being supported at another point in its length from said means, and means located externally of said line resonator and linked to said rod for enabling longitudinal movement of said rod within said inner conductor.

JAMES W. CONKLIN. LUDWIG A. BATTERMANN. 

